Server Version#: 1.14.1.5488
Player Version#: 3.83.1
Hello forum members, thanks in advance for your help with this one.
I’m running Plex Server and Media Player both on the same newly build HTPC, connected directly to my HDTV by HDMI, audio connected to my audio receiver using optical S/PDIF. Computer is an i5-8400, 32 GB ram, SSD boot disk and WD Red 4 TB disk storing my media. I use it primarily for over-the-air TV DVR functions.
The problem I’m having is that when I have direct play enabled along with AC3 pass-through the audio will randomly skip. Just for a fraction of a second, but enough that my audio receiver drops from DOLBY DIGITAL to 2-channel PRO LOGIC. And there is a fraction of a second with no audio. Super annoying.
Some additional background in case it helps in troubleshooting: I have found that disabling AC3 pass-through eliminates the problem, but I’m not convinced that I’m getting the full 5.1 channel audio this way, my receiver reports only left-right channels. Disabling direct play also fixes the problem, receiver reports DOLBY DIGITAL stream with no skipping, but then my computer CPU is pegged when watching anything, seems inefficient and should not be necessary.
I was able to find a few references to this same problem in the forums but they were older posts. I’m hoping someone has some new information. This seems to be a plex specific problem because I can watch the same video files in VLC with passthrough enabled and no problems at all. Receiver reports DOLBY DIGITAL with no drops or skips.
Any suggestions?
Thanks,
Mike
1 Like
Did you get anywhere with this. I’m having the same issue with 4k videos and the audio skip for just a split second at random points. I also did the VLC test and have the same findings. I’m also not convinced that the pcm it passes to the receiver is as good as the original track. I watched the same movie twice and had to turn it down with pass through on because it was clearer. And up with the pcm because it was muddy.
While the tracks are suppose to be lossless. I don’t think Plex is handling the decoding correctly. One is muddy the other is clear.
Any info you’ve gotten since this post would be super helpful.
I have not made any progress on this, it’s driving me crazy. I’ve changed every setting and every combination of settings with no benefit. The bottom line, if I enable AC3 passthrough then my audio receiver seems to lose lock on the signal at random which causes an audio skip for a fraction of a second. Nothing I do changes this, and I’ve done everything.
If I disable passthrough then it never skips, but then I lose full 5.1 surround sound. I have done several checks using Dolby Digital test video files. Without passthrough all the sound is there, but it loses position. In other words, it plays through the front speakers. My receiver uses Dolby Pro Logic II to try and add position back to the stereo signal but does a poor job compared to the original audio.
That sounds as if it’s to do with your TV passing the audio to the receiver. Why not connect your HTPC directly to your AVR?
Sorry, I wasn’t clear in my description. I am passing audio directly from the HTPC to the receiver using an S/PDIF optical cable. My old HTPC used this same method with no problems (an old Windows 7 box running windows Media Center). My newly built HTPC running plex connects with the same cable, direct from computer to receiver. I did replace the optical cable after this problem started, based on feedback on a few other forums, but no change. I’ve tried using a S/PDIF coaxial cable as well (computer and receiver both support both cable types). Also no change. I’ve even tried a dedicated sound card instead of the onboard audio, no change. I’m pretty convinced that this has to do with how Plex handles the audio as I don’t have the problem if watching videos using VLC.
Also, one other thing that may or may not be related. I’ve noticed that the audio and video get out of sync when watching a program. Audio gets ahead by a second over maybe 10 minutes. Super annoying, problem resets if I pause and restart. So that’s a manageable fix but still seems like this should not happen. I do have sync set to Audio.
Puzzling…
Mike
I literally have the exact same problems as you. To the T. I don’t want to let Plex handle decoding because I to think that audio is muddy.
HTPC > AVR > Projector.
We both are using HTPC to AVR. As a Plex employee are you going to dig into this?
Are you able to provide some logs that cover a time period when this happened, and state the approximate time playback was started, and what was playing? You can find more information about getting logs here.
Can you also add the other information that was requested, please?
Iron man 2 in HEVC DTS-HD MA. Around 7-8pm on 4/19. I think that was the time. Might have been 9. 
From what I can see in those logs, you’re attempting to passthrough TrueHD with SPDIF, which as far as I’m aware, isn’t possible. I believe you need to use HDMI to passthrough TrueHD or DTS-HD. It may also be an idea to turn on refresh rate switching, if your projector supports multiple refresh rates.
If you haven’t already, I suggest you have a look at these support articles.
https://support.plex.tv/articles/212072167-audio-configuration-guide-plex-media-player/
https://support.plex.tv/articles/115000473213-settings-plex-media-player/#toc-3
I’ve also attached logs. I watched a few minutes of Last Man Standing, then Pacific Rim, then Hawaii 5-0, on 4/23/2019, all right around 8:00 AM.
I noted audio skips within the first 30 seconds of both the TV programs (recorded using Plex DVR functionality), and did not this time observe an audio skip in Pacific Rim (Encoded with Handbrake), although I have used this file as a test before and have experienced audio skips so I know it still happens with this file.
In my case I am not passing TrueHD (as best I can tell), only 5.1 Dolby Digital.
Thanks,
Mike
PlexMediaPlayer.log.1.txt (247.4 KB)
PlexMediaPlayer.log.2.txt (1.0 MB)
PlexMediaPlayer.log.3.txt (1.0 MB)
PlexMediaPlayer.log.4.txt (1.0 MB)
PlexMediaPlayer.log.5.txt (1.0 MB)
PlexMediaPlayer.log.6.txt (101.5 KB)
PlexMediaPlayer.log.7.txt (445.3 KB)
PlexMediaPlayer.log.8.txt (1.0 MB)
PlexMediaPlayer.log.9.txt (1.0 MB)
PlexMediaPlayer.log (689.6 KB)
I can assure you i am not using SPDIF the only connection i have from the PC to the AVR is HDMI. So if there is a setting you would like me to change please let me know.
And i have been through both of those articles in excess trying to figure this out.
Can you play something, and during playback, bring up the debug overlay by pressing I, and take a screenshot of it please?
Two screen shots attached. From two different TV shows.
What i dont understand is why it calls it spdif-dts-hd when i am not even using that port. I run pure HDMI. And yes my cables are HDCP 2.2 HDMI 2.0.
